The invention relates to spraying systems, and more particularly to a method for spraying pesticides, herbicides, or the like in a moving path from above.
There is a need in many locations for efficient control of weeds and other vegetation growth. Such growth is often efficiently inhibited by application of chemicals, but in many locations there is no easy access for an herbicide-spraying truck to move alongside the path of the vegetation growth. This is also the case with chemcial pesticide, insecticide and fungicide application. Such chemicals are usually in liquid form but may also be in powder or granule form.
Aerial spraying with helicopters and light fixed-wing aircraft has been effective, but is expensive and hazardous and also requires special licensing or approval of the particular pesticide or herbicide for aerial application. One reason for such approval requirements is that when sprayed by aircraft, the materials tend to drift and affect unintended areas. The drift also leaves some areas unsprayed and some double-sprayed. The minimum height that can be flown in is limited, limiting accuracy.
With helicopters, the downdraft from the rotor blades can interfere with spraying and can damage fragile crops. All aerial spraying requires nearly ideal weather conditions.
Various apparatus have been suggested for vehicles for spray application of pesticides or herbicides or similar materials onto application paths alongside the moving vehicle. For example, trucks, sometimes with extendable booms, have been used for applying herbicides along the side of roadways to prevent excessive vegetation growth at the edge of the roadway. The reach of such apparatus is very limited.
Alongside drainage ditches, canals and other waterways there is often a need to control vegetation growth on a regular basis, usually done with chemical herbicides. Generally the waterway is too wide to spray both sides with a vehicle moving along one side, and in many cases even one side cannot be sprayed with the conventional moving vehicle, often because the line of vegetation to be controlled is too far away from an accessible travel path for the vehicle.
Accordingly, there has been a need particularly in the fields of vegetation control and pesticide application for a fast and efficient way of spraying materials from above, without the need for aircraft. Conventional equipment and methods have not provided the effectiveness and efficiency of the present invention described below.
U.S. Pat. No. 4,230,272 (Snell) discloses a form of spraying using a flexible apertured pipe stretched between two spaced-apart vehicles, for spraying the area between the vehicles. In one embodiment the patent shows a cable or wire tensioned between the vehicles and clipped onto a flexible apertured pipe, so that the pipe itself does not hold the supporting tension. The patent also discloses replacing one of the vehicles with a fixed structure at a pivot point, for spraying the area within a circle. However, the Snell patent utilizes a cable or pipe tensioning system which would be inadequate and inappropriate for purposes of the present invention described below.
Other patents having some pertinence to features of the present invention are U.S. Pat. Nos. 628,994, 4,014,516 and 4,386,759.